1. Field of the Invention
This invention relates to an improved intrauterine device wherein there is a cavity provided in at least a portion of the intrauterine device and a concentrated fluid solution of a drug providing antifibrinolytic, antifertility and antiproteolytic effect is provided within the cavity. The cavity walls are defined by a polymer having a predetermined permeability for the drug.
2. Description of the Prior Art
Many forms and configurations of intrauterine devices designed to prevent conception in the female have heretofore been utilized. Such devices have been provided in a variety of shapes, such as the "T" device shown in U.S. Pat. No. 3,533,406, the Loop, such as shown in U.S. Pat. No. 3,200,815, a "Y" configuration, generally termed a "Ypsilon" configuration, a ring or modified ring such as the Ota ring, and many modifications thereto, including flat, leaf-like members between various segments of the intrauterine device. Such intrauterine devices which were not provided with any medications associated therewith depended upon their presence in the uterus to prevent conception.
Further, other intrauterine devices (IUDs) have incorporated a controlled release rate medication or drug therein to further aid the anticonceptive action thereof. Such medicated IUDs have generally employed copper or progesterone as the contraceptive or antifertility agent. However, it has been found that copper-releasing intrauterine devices, as well as non-medicated intrauterine devices still resulted in pain and cramping to the wearer, as well as metrorrhagia and menorrhagia. Consequently, the excessive uterine hemorrage, with or without pain, continues to be a leading cause for this type of intrauterine device removal. The progesterone-releasing intrauterine devices are associated with significantly less bleeding than other devices but they appear to be associated with a serious complication apparently produced by the release of progesterone. This complication is ectopic pregnancy.
Nevertheless, the general convenience and safety of intrauterine devices continues to give hope that the IUD may one day provide an ideal method for worldwide population control, since it has been found, statistically, that intrauterine devices can provide effective contraception in a 98-99% range of effectivity, they do not require conscious effort, are less subject to human failings than any other type of contraceptive, their antifertility effect is completely reversible, they have minimal, if any systemic effect, and their effect is confined essentially to the uterus. However, it is believed that even greater antifertility effect can be achieved by utilizing other anticonception agents with an IUD, which agents do not have the serious detrimental side effects noted above.
Consequently, there has been a need for improved medicated intrauterine devices providing greater antifertility effect and in which the side effects of pain, metrorrhagia and/or menorrhagia are reduced or eliminated, and which are not associated with other serious side effects such as ectopic pregnancy.
While the inflammatory response of the endometrium to intrauterine devices has heretofore been known, I have discovered that the chronic response of the endometrium to long-term intrauterine device exposure is more a humoral type of reaction (accompanied by increased vascular permeability with edema and interstitial hemorrhage) than the immunologic or cellular type of response (accompanied by infiltration of immune complexes or of leukocytes, such as plasma cells or neutrophils). However, I have found that there are defects in small endometrial vessels which suggest damage caused by mechanical distortion of the uterine tissues. The defects generally lack hemostatic plugs of platelets and/or fibrin. Further, there is evidence that fibrinolysis is activated in the uterus in response to the presence of an intrauterine device. This activation could result in blockage of normal hemostatic reaction at several levels in the coagulation system. Further, it may initiate, aid, or aggravate humoral inflammation by any one or all of the following mechanisms:
1. Activation of the complement system and histamine release; PA1 2. Activation of prekallikrein; and PA1 3. Release of fibrin degradation fragments.
Histamine can cause vascular dilation and increase vascular permeability. Kallikrein (activated prekallikrein) releases bradykinin which can have an effect similar to histamine and may also cause cramping and pain. Fibrin degradation fragments may enhance the vascular effects of histamine and bradykinin. Combined with distortion of the endometrium caused by myometrial contractility around the relatively inelastic or unyielding IUD, which may also be associated with increased prostaglandin synthesis and release, it may be predicted that excessive bleeding from leaky or broken vessels will occur. For these reasons, incorporation into medicated IUD devices of potent inhibitors of plasminogen activation and plasmin activity (fibrinolytic activity) for the purposes of intrauterine release over an extended time period can provide an alleviation of the aforesaid undesired effects.
It has also heretofore been found that IUD associated uterine hemmorhage can be alleviated by the systemic (oral) intake of the fibrinolytic inhibitors epsilon aminocaproic acid (EACA) and tranexamic acid. I have also demonstrated that an EACA loaded IUD inserted into the uterus of rhesus monkeys provides an ameliorative effect on menstral blood loss, and there was no apparent systemic effect by such medicated devices on fibrinolytic activity in these animals. However, neither EACA nor tranexamic acid would appear to be satisfactory agents for long-time intrauterine medication. First, they are not highly potent anti-fibrinolytic agents and would have to be delivered at a rather high rate into the uterine cavity. Thus, a drug loaded IUD would become exhausted of its medication in a short period of time, or would require an unacceptably large size of device. In addition, EACA and tranexamic acid are small molecules which are highly diffusible and water soluble. Therefore, intrauterine release thereof from a medicated intrauterine device at a steady, constant rate is difficult to control and effective concentrations inside the uterus difficult to maintain. Consequently, inhibitor concentrations of either EACA and tranexamic acid of between 1.times.10.sup.-3 and 1.times.10.sup.-4 Mol/liter, which is the concentration of these drugs required to be effective, respectively, over a prolonged period of time is generally not achievable considering the amount of medication which is feasible to load into an IUD and considering the diffusion and solubility properties of these compounds and the rate of water turnover inside the uterus.
While there heretofore has been some indication that certain compounds used for treatment of protozoal, bacterial and fungal infections may have anti-fibrinolytic properties, there has not heretofore been any indication of anti-fertility action of these compounds added to an intrauterine device. These compounds may be generally defined as the aromatic amidines, and in particular, the aromatic diamidines. However, heretofore, it has not been specifically recognized that their anit-fibrinolytic action inside the uterus can alleviate the metrorrhagia and menorrhagia. Further, even though such metrorrhagia and menorrhagia may be alleviated, the pain and cramps associated with intrauterine devices could still remain a major drawback to effective extensive use of medicated intrauterine devices as a population control technique.
In addition to the above-mentioned types of intrauterine devices, there is also heretofore been provided intrauterine devices in which all or a part of the device is hollow and thus the device has walls defining the cavity. Such a device is shown, for example, in U.S. Pat. No. 3,896,819 and other types of such devices are shown, for example, in U.S. Pat. No. 3,710,795 in which the cavity is filled with a solid matrix, and other prior art patents. Similarly, there have heretofore been proposed inflatable intrauterine devices in which the walls of the intrauterine device are flexible and it is inserted into the uterus in uninflated condition and subsequently expanded.
However, in none of the prior art devices has there heretofore been provided a drug releasable at a controlled rate over an extended period of time which drug provides not only an antiproteolytic action but an enhanced contraceptive action. Accordingly, there has long been a need for an intrauterine device which can provide the above desiderata.
Additionally, in many prior art IUDs, expulsion thereof is a somewhat frequent occurrence. Such undesired expulsion is another drawback of prior art IUDs.
Consequently, there has long been a need for a medicated intrauterine device which not only enhances the anti-fertility action of the IUD but also provides reduction or elimination of metrorrhagia or menorrhagia for an extended period of time, as well as decreasing the pain and cramps associated with wearing an intrauterine device, as well as decreasing the tendency of expulsion thereof.